diy fountain tiles popping up

I did a half circle shape English trough fountain using cement, sand, and spagham moss. It cured for about an entire year. I recently mosaic the fountain with glass pebbles and 2 x 2 tiles. I used mastik thinset and then grouted with a sandy grout. My first problem was a hairline fracture near the top of the fountain that is full of glass pebbles. How can I correct this hairline fracture as it keeps slowly growing sidewise.

My second question is I stopped the fountain about a month ago and noticed on the far left side my bottom tiles were popping up in a corner and the mastik is exposed and forming a clumpy deteriorated milky clumps. How can I fix this problem? I ran the fountain for about two months without noticing any tiles popping up until I stopped the water from flowing and had standing water and then I noticed my tiles had popped up with the mastik being exposed.

Any suggestions will be greatly appreciated.

[Floorguy]

LOL!!

Tear it all off and scrape that junk mastic off and scrub the surface pores to open them up.

Then get you a bag of real mortar, and not mastic to set the tiles and pebbles again.

[cproader]

Floorguy said LOL!! Tear it all off and scrape that junk mastic off and scrub the surface pores to open them up. Then get you a bag of real mortar, and not mastic to set the tiles and pebbles again.

.............he's alittle testy......he was knockin on the Pearly Gates last week, and they didn't let him in.................BUT HE'S RIGHT !!!...wrong place to use nastic..........

[Kman]

Mastic is definitely not made for a wet area, especially if the tiles are submerged. I'm kind of surprised it held as long as it did. I can count on one hand the number of times in the past year I used mastic. It will re-emulsify when continually exposed to water.

You will need to clean the mastic off and let the tile dry, like Floorguy said. I would get the best modified mortar I could find. Let it cure for three to four weeks before grouting, just to be safe.

real mortar? what name am I to look for? LOL???? I did the outside and inside with the mastik. Don't they use mastik for bathroom shower jobs? Is that the wrong medium for adhearing when water is concerned? If you know the right name for full water contact, please let me know. Thanks for your two responses. LPonzio

[Jerry Thomas]

Without a membrane or liner applied over the cement/sand base I'm surprised the fountain has not leaked yet. That could a reason you have a crack by moisture getting behind the mastic.

For problematic installs I have been using Mapei's Kerabond thinset mortar with the Keralastic additive. http://www.mapei.it/Referenze/Multim...tic_TDS_EA.pdf

[Kman]

I did the outside and inside with the mastik. Don't they use mastik for bathroom shower jobs? Is that the wrong medium for adhearing when water is concerned? If you know the right name for full water contact, please let me know

You will find that some installers use mastic for wet areas, including showers......but they shouldn't. The manufacturers of mastic will state a number of applications where it can be used, including some floor applications, but I wouldn't trust any of them. The only place I'll use it is on a kitchen backsplash, and sometimes I won't even use it there. I don't know of any mastic manufacturer that will endorse their product for a wet area, including a shower.

As far as the brand of thinset mortar you'll use, it'll kind of depend on what's available to you from your local retailer. What you're looking for is a modified thinset. Just because it's a costly brand doesn't necessarily mean it's the best, but expect to pay somewhere between $20 and $30 for a 50 lb. bag. The brand Jerry gave you is good, but it's really a matter of what you can find.

As far as the liner.....ugh. If you didn't use one, you're likely to have long term problems.

[Bud Cline]

I did a half circle shape English trough fountain using cement, sand, and spagham moss.

That particular recipe ( commonly referred to as "TUFA") is not the best foundation for what you are trying to do. I doubt any thinset will hold the tiles for very long.

TUFA was never intended to be tiled as far as I know.